This invention provides indazoles that are useful in the treatment or inhibition of LXR (Liver X receptor) mediated diseases, e.g., cardiovascular diseases, a process for preparing them, and pharmaceutical compositions containing them.
Atherosclerosis, a complex disease of lipid disorder and inflammation, is the leading cause of death in developed countries. A number of independent risk factors have been identified and the most notable are high levels of serum LDL cholesterol and low HDL cholesterol. Although the most effective therapies such as statins have been shown to lower LDL cholesterol significantly (20-60%), still most patients experience adverse coronary events. Also, statins have their own undesirable side effect profile (myotoxicity), which prevents many patients from taking them. Therefore, additional therapeutic strategies to not only decrease LDL cholesterol, but also to increase HDL cholesterol, are critically needed. The important reason to increase HDL cholesterol is to increase cholesterol transport from peripheral tissues to liver for metabolism and excretion. This function of transporting cholesterol from periphery to liver is called reverse cholesterol transport and HDL plays a major role in this pathway. In addition, HDL has been suggested to inhibit the oxidation of LDL cholesterol, reduce the inflammatory response of endothelial cells, inhibit the coagulation pathway and promote the availability of nitric oxide. The key transporter involved in HDL production and reverse cholesterol transport is ABCA1. Therefore, upregulation of ABCA1 results in increased reverse cholesterol transport as well as inhibition of cholesterol absorption in the gut.
LXRs, originally identified from liver as orphan receptors, are members of the nuclear hormone receptor super family and are involved in the regulation of cholesterol and lipid metabolism. They are ligand-activated transcription factors and bind to DNA as obligate heterodimers with retinoid X receptors. While LXRα is restricted to certain tissues such as liver, kidney, adipose, intestine and macrophages, LXRβ displays a ubiquitous tissue distribution pattern. Activation of LXRs by oxysterols (endogenous ligands) in macrophages results in the expression of several genes involved in lipid metabolism and reverse cholesterol transport, including ABCA1, ABCG1 and ApoE. Studies have been conducted in LXRα k/o, LXRβ k/o and double k/o mice to determine the physiological role of LXRs in lipid homeostasis and atherosclerosis. The data indicate that in double k/o mice on normal chow diet, increased cholesterol accumulation was observed in macrophages (foam cells) of the spleen, lung and arterial wall. This was associated with reduced serum HDL cholesterol and increased LDL cholesterol despite normal total cholesterol levels. While LXRα k/o mice did not show significant changes in hepatic gene expression, LXRβ k/o mice showed a 58% decrease in hepatic ABCA1 expression and a 208% increase in SREBP1c expression, suggesting that LXRβ may be involved in the regulation of liver SREBP1c expression. Agonists of LXRαor β are very effective in upregulating ABCA1 expression (desirable effect) in macrophages. The biological activities of several agonists have been shown in two atherosclerotic mouse models (ApoE k/o and LDLR k/o). Treatment of these mice with agonists for 12 weeks resulted in significant inhibition of atherosclerotic lesions. While these two compounds had variable effects on serum cholesterol and lipoprotein levels, both compounds caused a significant increase in serum HDL cholesterol and triglyceride levels. These in vivo data agree well with the in vitro data obtained for the compounds in macrophages.
In addition to the lipid and triglyceride effects described above, a very recent communication in Nature Medicine (9: 213-219, 2003) presents convincing data that activation of LXRs results in the inhibition of inflammation and proinflammatory gene expression in three different models of inflammation (LPS-induced sepsis, acute contact dermatitis of the ear and chronic atherosclerotic inflammation of the artery wall). These data suggest that LXR modulators can mediate a two-pronged effect (removal of cholesterol from the macrophages and inhibition of vascular inflammation) resulting in the inhibition of atherosclerotic lesions.